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Difference between single and double square brackets in Bash
...nt of [ that prevents further arguments from being used.
Ubuntu 16.04 actually has an executable for it at /usr/bin/[ provided by coreutils, but the bash built-in version takes precedence.
Nothing is altered in the way that Bash parses the command.
In particular, < is redirection, && a...
How to automatically install Emacs packages by specifying a list of package names?
...a list of package names in .emacs file and then package could automatically search and install the packages, so that I don't need to install them manually by calling M-x package-list-packages . How to do that?
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Using python map and other functional tools
...earn. A fundamental rule in functional programming is that every time you call a function with the same arguments, you ALWAYS get the same output. This avoids a vipers nest of bugs introduced by having global state. As maptest depends on an external definition of bars, this principle is broken.
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Avoiding instanceof in Java
...is entry from Steve Yegge's Amazon blog: "when polymorphism fails". Essentially he's addressing cases like this, when polymorphism causes more trouble than it solves.
The issue is that to use polymorphism you have to make the logic of "handle" part of each 'switching' class - i.e. Integer etc. in ...
Why use a prime number in hashCode?
...ly be determined by the least significant entry (the one not multiplied at all). Similar entries will collide. Not good for a hash function.
31 is a large enough prime that the number of buckets is unlikely to be divisible by it (and in fact, modern java HashMap implementations keep the number of b...
Microsecond timing in JavaScript
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As alluded to in Mark Rejhon's answer, there is an API available in modern browsers that exposes sub-millisecond resolution timing data to script: the W3C High Resolution Timer, aka window.performance.now().
now() is better tha...
Why is there no String.Empty in Java?
...would save on compile time, in fact I think it would be the latter.
Especially considering Strings are immutable, it's not like you can first get an empty String, and perform some operations on it - best to use a StringBuilder (or StringBuffer if you want to be thread-safe) and turn that into a Str...
check if a std::vector contains a certain object? [duplicate]
Is there something in <algorithm> which allows you to check if a std:: container contains something? Or, a way to make one, for example:
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SQL command to display history of queries
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try
cat ~/.mysql_history
this will show you all mysql commands ran on the system
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What does the comma operator , do?
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then if I write i = (5,4,3,2,1,0) then ideally it should return 0, correct? but i is being assigned a value of 5? Can you please help me understand where am I going wrong?
– Jayesh
Nov 13 '10 at 6:55
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